Process for the production of permanent creases in cellulosic textiles utilizing inorganic salt solutions



United States Patent 3,268,291 PROCESS FOR THE PRODUtITlON 0F PERMA- NENT CREASES IN CELLULOSIC TEXTILES UTILIZING INORGANIC SALT SOLUTIONS Charles H. Mack and Clinton P. Wade, New Orleans, La., assignors to the United States of America as represented by the Secretary of Agriculture No Drawing. Filed Sept. 14, 1962, er. No. 223,853 Claims. (Cl. 8-116) A non-exclusive, irrevocable, royalty-free license in the invention herein described, throughout the world for all purposes of the United States Government with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

This invention relates particularly to a process for placing durable localized creases in textiles that have been resin-finished for the purpose of inducing wrinkle-resistance. Although the process of this invention can be employed to place durable creases in textiles that have received no wrinkle-resistant resin-finish whatsoever, from a practical standpoint application of the process for placing durable creases in resin-finished textiles is the important utility.

Considerable amounts of cotton, viscose rayon, and blends of cotton and rayon are treated with compounds and resin formers to impart such properties as dimensional stability, rapid drying, wrinkle-resistance, and wash-andwear qualities. These textiles are generally referred to as resin-finished or resin-treated textiles and the terms resinfinish, resin-finished, resin-treated or resin-treatment are used in this sense hereinafter. Resin-treated textiles have been found useful in nearly all types of outer garments. There exists, however, a serious problem in the use of resin-treated textiles for the construction of wearing apparel. It is difiicult or impossible to place satisfactory permanent creases at locations where creases are desirable, by using conventional steam-pressing techniques. This fact has discourage the use of resin-treated textiles for the fabrication of shirts, blouses, pleated skirts and blouses, and especially trousers, because without creases at the desired locations, the appearance of such garments is unsatisfactory.

Prior to the development of the process herein described, two methods have been available for the production of garments with durable creases. The first method involves resin-treatment of the fabricated garment without curing. The resin-treated garment is subsequently cured by ironing and creases are placed concurrently where desired. That is, of course, an awkward, costly method for resin-finishing and creasing garments. An alternative method, also well known, is to crease the resin-treated and cured garment by applying a solution of an acid catalyst to the portion of the cloth to be creased and then heating to set the crease by use of a hand iron. This method is applicable only to N-methylol type resins. The catalysts employed in this latter method are strong acids (such as hydrochloric acid) or acid salts (such as zinc nitrate) 32%,291 Patented August 23, 1966 which give rise to strong acids. It is theorized that with this method the acid solution of the catalyst partially hydrolyzes the crosslinked cellulose (the resin polymer and/or cellulose bonds are broken) and, subsequently, new cross-links are established under the influence of heat and the catalyst when the textile is ironed dry. Hot acid treatment, of course, seriously weakens the textile since cellulose itself is easily hydrolyzed by strong acids. A third method has recently been discovered in which the durable creases are placed in resin-finished cellulosic textiles and garments by the use of alkaline swelling agents. The mode of application is similar to the preceding method in that the portion of the cloth to be creased is treated with an alkaline swelling agent such as mercerizing strength sodium hydroxide solution and the resulting swollen fabric is heated to set the crease by use of a hand iron.

An object of this invention is to provide a process for placing durable creases in resin-finished cellulosic textiles and garments by the use of solutions of certain inorganic salts which are known to be swelling agents for cellulosic materials.

In general, the process of this invention comprises wetting a resin-finished cellulosic textile with a 7% (by weight) to saturated aqueous solution of certain inorganic salts which are known to swell cellulose and then setting a crease by the application of heat and pressure to the desired crease location. More specifically the process of the invention comprises wetting a resin-finished cellulosic textile at and near the location of intended crease with a solution containing about from 7% by weight to saturation of a dissolved inorganic salt and then applying simultaneously heat at about from to 250 -C. and pressure of at least about one fourth pound per square inch to the wetted area until the wetted are is essentially dry.

The process of this invention is particularly useful for placing durable creases in garments that are made from resin-finished piece goods, but it is also useful as a means for removing the puckering that so often occurs at the seams and at the pockets of garments made from resinfinished fabrics. The creases produced by this process are remarkably durable and they will resist repeated launderings.

Textile fabrics suitable for use in practicing this invention include resin-finished cotton, viscose rayon, ramie, jute and the like cellulosic textiles. The textile may or may not be dyed. Cotton fabrics which have not been resin-finished are also suitable. Nonresin-finished cotton fabrics at any stage of wet processing-gray, scoured, scoured and bleached, or scoured, bleached, and mercerizedcan be given durable creases according to the processes set forth in this invention. When cotton fabrics are to be creased, resin-finished or not, prior mercerization is desirable. If the cotton fabric is resin-finished, mercerization should precede the resin treatment. If cotton fabrics are not mercerized before creasing, and if only the area to be creased is wet with the inorganic salt solution, a visible difference in the translucency of the fabric at or near the crease will occur. If the entire fabric is wet with the inorganic salt solution, this difference does not occur.

The process of this invention finds particularly valuable utility for placing durable creases in textile fabrics finished with compounds or resins that impart wrinkle resistance. Examples of durable resin-finishing agents with which the creasing technique of this invention is compatible include polyepoxy compounds, polyacetal compounds, tetrakis (hydroxymethyl) phosphonium chloride in the presence of amines or amides, tetrakis (hydroxymethyl) phosphonium chloride in the presence of tris (l-aziridinyl) phosphine oxides, 'tris (l-aziridinyl) phosphine oxide used alone or with modifiers, carbonyl bisaziridine, formaldehyde, methylol phenols, dimethyloltriazones, dimethylol ethylene urea, l,3-dichloropropanel-2, and the like compounds. Certain of the resin finishes for textiles listed above as compatible with the creasing technique of this invention will be recognized by those skilled in the art not only as wrinkle-resistant but, also as well, flame-resistant. The listed resin finishes are merely examples that show the wide range of materials useful to impart wrinkle resistance into cellulosic textiles and in turn compatible with the creasing process of this invention. The list is not intended to be allinclusive.

Substantially any inorganic salt solution capable of swelling cellulose can be used in the creasing process. Illustrative examples of suitable inorganic salts include: the thiocyanates of barium, calcium, strontium, and manganese; the halides of calcium, strontium, and lithium; and mixtures of any one or more of the abovementioned salts. This list is not intended to be all-inclusive. The use of lithium chloride, lithium bromide, calcium thiocyanate and mixtures of these salts is preferred. Water solutions ranging in concentration of inorganic salt from about 15% to saturated are preferred. It is desirable to allow the aqueous inorganic salt solution to remain in contact with the fabric for about ten seconds before applying heat and pressure to produce the crease. The addition of a wetting agent to the inorganic salt solution is sometimes desirable to insure thorough and rapid penetration of the solution into the fabric.

The heating and pressingdn of the crease may be accomplished in a number of ways. The preferred procedure is to first press-in a temporary crease by a conventional procedure, then wet the crease with a solution of the inorganic salt and, finally, apply heat and pressure to the wet crease until the wetted area is essentially dry. The pressing-in of the temporary crease is not essential to the process but such a procedure assures correct positioning of the durable crease. The hand iron is a convenient instrument for applying the heat and pressure. The creasing temperature may range from as low as 100 C. up to about 250 C. The preferred range of temperature is from about 120 C. to 200 C. In all cases the textile is heated until the creased area is essentially dry. By the languageessentially drywe mean that the texile should, after creasing and pressing, contain not more than about 15% moisture in the area of the crease. The greater the amount of pressure applied the sharper will be the finished crease, the minimum pressure should be not less than about one fourth pound per square inch. Creases placed by the process of this invention are not removed by laundering, and can only be removed by again wetting the creasing area with a solution of the inorganic salt and applying heat and pressure to the opened crease. The process may in some cases cause slight discoloration of the textile, but the discoloration of the textile resulting from crease placement by the procedure set forth in this invention is readily removed when the textile is laundered.

The sharpness of the permanent creases developed in the textile using the procedure set forth in this invention is not only accomplished by varying the pressure applied to the creased area but also to the property of the salt solution. In all cases, however, the crease whether sharp or not is permanent and withstands many launderings.

There is no evidence that the inorganic salt is chemically bound to the cellulose because it is readily washed out in the final water washing step. Consequently, none of the salt is consumed in the process and may, if warranted, be recovered from the rinse solutions.

For the purpose of demonstrating that the creasing process of this invention does not require or even involve the resins employed in resin-finishing of textiles, the following experiments were carried out:

A piece of 4-02. desized and bleached x 80 cotton print cloth was creased .by pressing with a hot iron. With the aid of an eyedropper a streak of 30% lithium chloride solution was placed along the crease. After about ten seconds the fabric was creased again along the previous crease by pressing with a hot iron. The area along the crease which had been saturated with the inorganic salt solution turned stiff. The fabric was then immersed in a water bath and then washed with hot water for 30 minutes. The fabric was then air dried. This crease was good and sharp although a slight puckering about the crease persisted. This was due to the slight shrinkage of the fabric along the crease.

A sample of mercerized 80 x 80 cotton print cloth subj cted to the same crease treatment yielded similar results as well as a sample of 48 x 48 cotton sheeting and broadcloth.

Example 1 A piece of 4-02. desized and bleached 80 x 80 cotton print cloth was resin-finished with tris (l-aziridinyl) phosphi ne oxide (a durable finishing agent useful for flame proofing as well as for wrinkle proofing). The finished fabric contained about 8.2% resin. The intended location for a crease in the resin-finished fabric was marked by pressing with a hot iron. The thus superficially creased area was wetted with a 60% aqueous calcium ithiocyanate solution which had been saturated with lithium chloride using an eyedrop-per. The area was then permanently creased by pressing until dry with a hot iron. Pressing temperature was kept at least C. and imposed pressure at least one fourth pound-per square inch. The fabric was then immersed in a hot water bath and rinsed with hot running water for thirty minutes, after which the fabrics was air dried. The crease was good and sharp with very little puckering existing about the crease. The creased textile withstood five home type washing cycles without diminished crease appearance.

Example 2 The following table flists the inorganic salt solutions as well as the pre-treatment of 80 x 80 print cloth used in imparting permanent creases. The procedure for applying the permanent crease was essentially the same as that described in Example 1. The creases were rated siibjectively as poor, fiair, good, excellent and the symbols P, F, G, and E are used to represent these ratings in the following table. The ratings remained the same after the fabrics and creases were subjected to five laundry cycles.

RATING OF PERMANENT CREASES APPLIED TO RESIN FINISHED COTTON FABRICS WITH INORGANIC SALT SOLUTIONS I Inorganic Salt Solution Calcium Thiocyanate Pre-Treatment or Mixture Y Resin Finish Lithium Lithium Calcium Calcium Chloride, Bromide, Thiocyanate, Iodide,

% 80% 60% With With 60% Lithium Lithium Chloride Bromide Dimethylol ethylene G E G E F.

urea. Tris(1-aziridinyl) P G. G. E E P phosphine oxide. Dimethylol ethyl P- G P P.

triazone. Formaldehyde G. E P. Acetal 1 F G. P 1,32 dichloropropanol- F F F.

1 All treatments were carried out on 80 x 80 cotton print cloth with the exception of 1,3 dichloropropanol-2 sample which was broadcloth.

2 Solutions were prepared by dissolving the lithium salt in 60% calcium thiocyanate solution until saturated.

3 Fabric contained 1.8% resin. 4 Fabric contained 8.2% resin. 5 Fabric contained 7.0% resin.

5 Mercerized fabric containing 1.35% formaldehyde having wet and dry wrinkle recovery angle (W+F) of 318 and 284, respectively.

1 Fabric contained 6.5% glycol polyacetal resin. 5 Commercial sample treated with Belfast finish.

Example 3 Permanent creases were applied to 80 x 80 cotton print cloth as described in Example 1 using different concentrations of calcium thiocyanate solutions and lithium chloride solutions. Results are as follows:

1. A process for installing a permanent crease in a cellulosic textile comprising wetting the cellulosic textile in the area to be creased with an aqueous solution containing at least about 7% by weight of an inorganic salt capable of swelling cellulose and selected from the group consisting of calcium thiocyanate, lithium bromide, lithium chloride, and calcium iodide, and creasing the thus- Wetted area of the textile with pressure and heating until the textile contains not more than about 15% moisture in the area of the crease.

2. The process of claim 1 wherein the inorganic salt is calcium thiocyanate.

3. The process of claim 1 wherein the inorganic salt is lithium bromide.

4. The process of claim 1 wherein the inorganic salt is lithium chloride.

5. The process of claim 1 wherein the inorganic salt is calcium iodide.

6. A process for installing a permanent crease in a cellulosic textile comprising Wetting the cellulosic textile in the area to be creased with an aqueous solution containing about from 7 weight percent of an inorganic salt capable of swelling cellulose and selected from the group consisting of calcium thiocyanate, lithium bromide, lithium chloride, and calcium iodide, to the weight percent required to saturate the aqueous solution with respect to the inorganic salt, and creasing the thus-wetted area of the textile with pressure and heating until the textile contains not more than about 15% moisture in the area of the crease, the pressure being at least about one quarter pound per square inch and the heating temperature being at least C.

7. The process of claim 6 wherein the aqueous solution contains about 60 weight percent of calcium thiocyanate and a sufiicient amount of a member selected from the group consisting of lithium chloride and lithium bromide to saturate said aqueous solution with respect to the dissolved inorganic salts.

8. A process for installing a permanent crease in a resin treated cellulosic textile comprising wetting the resin treated cellulosic textile in the area to be creased with an aqueous solution containing about 60 weight percent of calcium thiocyanate and a sufiicient amount of an inorganic salt capable of swelling cellulose and selected from the group consisting of lithium chloride and lithium bromide to saturate the said aqueous solution with respect to the dissolved inorganic salts and creasing the thus-wetted area of the cellulosic textile with pressure and heating until the textile contains not more than about 15% moisture in the area of the crease, the pressure being at least about one quarter pound per square inch and the heating temperature being at least about 100 C.

9. The process of claim 8 wherein the inorganic salt is lithium chloride.

10. The process of claim 8 wherein the inorganic salt is lithium bromide.

References Cited by the Examiner UNITED STATES PATENTS 1,333,465 3/1920 Clayton 8-116 1,482,076 1/1924 Fourneaux 8-116 2,957,746 10/1960 Buck 8-116.3 3,113,826 12/1963 Daul et al. 8120 FOREIGN PATENTS 488,095 6/ 1938 Great Britain.

518,872 3/1940 Great Britain.

565,337 11/1944 Great Britain.

OTHER REFERENCES McKelvey et al., Journal of Polymer Science, vol. 51, pp. 209-230 (1961).

Reeves et al., American Dyestuff Reporter, vol. 48, No.21, pp. 4346 and 50 (1959).

NORMAN G. TORCHIN, Primary Examiner. JULIAN S. LEVITT, Examiner.

I. C. CANNON, Assistant Examirrer. 

1. A PROCESS FOR INSTALLING A PERMANENT CREASE IN A CELLULOSIC TEXTILE COMPRISING WETTING THE CELLULOSIC TEXTILE IN THE AREA TO BE CREASED WITH AN AQUEOUS SOLUTION CONTAINING AT LEAST ABOUT 7% BY WEIGHT OF AN INOGANIC SALT CAPABLE OF SWELLING CELLULOSE AND SELECTED FROM THE GROUP CONSISTING OF CALCIUM THIOCYANATE, LITHIUM BROMIDE, LITHIUM CHLORIDE, AND CALCIUM IODIDE, AND CREASING THE THUSWETTED AREA OF THE TEXTILE WITH PRESSURE AND HEATING UNTIL THE TEXTILE CONTAINS NOT MORE THAN ABOUT 15% MOISTURE IN THE AREA OF THE CREASE. 